But, their job isn't about standing around. It's about running into buildings. So, he took to the stairs to show us just how hot it can get. After two trips, we checked the thermometer inside his coat.

"108 degrees," he said. "Almost an 18 degree difference." And he's not even fighting a fire.

"People on the ambulances will come and refresh us, make sure we have fluids," Kopp explained.

Outside, Nancy Kluck has a different kind of uniform.

"I stay hydrated and keep walking," Kluck said.

She has worked for the United States Postal Service for 14 years. And she is no stranger to the elements, walking 5 to 6 hours a day no matter what the weather brings.

"You see it says 90 plus the next two days and then 80 after that, you look forward to those days," Kluck said.